6 files changed, 27 insertions, 9 deletions
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index 2c8a996cdb0..fff54814a38 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -136,11 +136,16 @@ fn call_intrinsic(cx: &ExtCtxt<'_>,
                   intrinsic: &str,
                   args: Vec<P<ast::Expr>>)
                   -> P<ast::Expr> {
-    if cx.current_expansion.mark.expn_info().unwrap().allow_internal_unstable {
+    let intrinsic_allowed_via_allow_internal_unstable = cx
+        .current_expansion.mark.expn_info().unwrap()
+        .allow_internal_unstable.map_or(false, |features| features.iter().any(|&s|
+            s == "core_intrinsics"
+        ));
+    if intrinsic_allowed_via_allow_internal_unstable {
         span = span.with_ctxt(cx.backtrace());
     } else { // Avoid instability errors with user defined curstom derives, cc #36316
         let mut info = cx.current_expansion.mark.expn_info().unwrap();
-        info.allow_internal_unstable = true;
+        info.allow_internal_unstable = Some(vec![Symbol::intern("core_intrinsics")].into());
         let mark = Mark::fresh(Mark::root());
         mark.set_expn_info(info);
         span = span.with_ctxt(SyntaxContext::empty().apply_mark(mark));
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 6bb7ee1d5dd..1b17fc0d040 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -711,7 +711,7 @@ pub fn expand_format_args_nl<'cx>(
     //if !ecx.ecfg.enable_allow_internal_unstable() {
 
     // For some reason, the only one that actually works for `println` is the first check
-    if !sp.allows_unstable()   // the enclosing span is marked as `#[allow_insternal_unsable]`
+    if !sp.allows_unstable("format_args_nl") // the span is marked as `#[allow_insternal_unsable]`
         && !ecx.ecfg.enable_allow_internal_unstable()  // NOTE: when is this enabled?
         && !ecx.ecfg.enable_format_args_nl()  // enabled using `#[feature(format_args_nl]`
     {
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index 7d7fd030859..05c8084a51e 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -61,7 +61,7 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
                      NormalTT {
                         expander: Box::new($f as MacroExpanderFn),
                         def_info: None,
-                        allow_internal_unstable: false,
+                        allow_internal_unstable: None,
                         allow_internal_unsafe: false,
                         local_inner_macros: false,
                         unstable_feature: None,
@@ -104,7 +104,9 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
              NormalTT {
                 expander: Box::new(format::expand_format_args),
                 def_info: None,
-                allow_internal_unstable: true,
+                allow_internal_unstable: Some(vec![
+                    Symbol::intern("fmt_internals"),
+                ].into()),
                 allow_internal_unsafe: false,
                 local_inner_macros: false,
                 unstable_feature: None,
@@ -114,7 +116,9 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
              NormalTT {
                  expander: Box::new(format::expand_format_args_nl),
                  def_info: None,
-                 allow_internal_unstable: true,
+                 allow_internal_unstable: Some(vec![
+                     Symbol::intern("fmt_internals"),
+                 ].into()),
                  allow_internal_unsafe: false,
                  local_inner_macros: false,
                  unstable_feature: None,
diff --git a/src/libsyntax_ext/proc_macro_decls.rs b/src/libsyntax_ext/proc_macro_decls.rs
index 24d09514520..5730081ce01 100644
--- a/src/libsyntax_ext/proc_macro_decls.rs
+++ b/src/libsyntax_ext/proc_macro_decls.rs
@@ -333,7 +333,10 @@ fn mk_decls(
         call_site: DUMMY_SP,
         def_site: None,
         format: MacroAttribute(Symbol::intern("proc_macro")),
-        allow_internal_unstable: true,
+        allow_internal_unstable: Some(vec![
+            Symbol::intern("rustc_attrs"),
+            Symbol::intern("proc_macro_internals"),
+        ].into()),
         allow_internal_unsafe: false,
         local_inner_macros: false,
         edition: hygiene::default_edition(),
diff --git a/src/libsyntax_ext/test.rs b/src/libsyntax_ext/test.rs
index 832bebb6113..37186246548 100644
--- a/src/libsyntax_ext/test.rs
+++ b/src/libsyntax_ext/test.rs
@@ -66,7 +66,10 @@ pub fn expand_test_or_bench(
             call_site: DUMMY_SP,
             def_site: None,
             format: MacroAttribute(Symbol::intern("test")),
-            allow_internal_unstable: true,
+            allow_internal_unstable: Some(vec![
+                Symbol::intern("rustc_attrs"),
+                Symbol::intern("test"),
+            ].into()),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),
diff --git a/src/libsyntax_ext/test_case.rs b/src/libsyntax_ext/test_case.rs
index 63417b702d5..1ed1ab0a07b 100644
--- a/src/libsyntax_ext/test_case.rs
+++ b/src/libsyntax_ext/test_case.rs
@@ -41,7 +41,10 @@ pub fn expand(
             call_site: DUMMY_SP,
             def_site: None,
             format: MacroAttribute(Symbol::intern("test_case")),
-            allow_internal_unstable: true,
+            allow_internal_unstable: Some(vec![
+                Symbol::intern("test"),
+                Symbol::intern("rustc_attrs"),
+            ].into()),
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition: hygiene::default_edition(),